1. Field of the Invention
The present invention concerns a subtractor/amplifier circuit incorporated into a fractionated analog-digital converter. This circuit enables the conversion of an analog signal into a high-precision digital signal, with a large number of bits, despite the limitation imposed by the resolution of the analog-digital converter (ADC).
2. Description of the Prior Art
In all known converters, irrespectively of their principle, the "significance" of the input analog signal is assessed by comparison with signals of known "significance". The greater the precision desired, that is, the greater the number of output bits desired, the smaller is the (constant) interval between the significance values. There comes a limit for which the interval, which represents the sensitivity or resolution of the ADC, is below the threshold voltage of the transistors forming the measurement circuits.
To cross this limit, the fractionated ADCs, which are known, isolate that part of the analog signal which is below the threshold voltage, amplify it and deliver the least significant bits with a degree of precision that could not possibly have been achieved otherwise.